CHALLENGES FOR STELLAR EVOLUTION AND PULSATION THEORY Jadwiga Daszyńska-Daszkiewicz Instytut Astronomiczny, Uniwersytet Wrocławski, POLAND JENAM Symposium "Asteroseismology and stellar evolution" September 8, 2008, Vienna

DIVERSITY OF STELLAR PULSATION J. Christensen-Dalsgaard

ASTEROSEISMOLOGY mode identification: osc →(n,,m) Amplitude frequency [c/d] mode identification: osc →(n,,m) ASTEROSEISMOLOGY

SEISMIC MODEL j,obs=j,cal(nj , j , mj , PS ,PT) PS -- parameters of the model: the initial values of M0, X0, Z0, the angular momentum (or Vrot,0 ), age (or logTeff ) PT -- free parameters of the theory: convection, overshooting distance, parameters describing mass loss, angular momentum evolution, magnetic field

SOME OBSERVATIONAL KEY PROBLEMS

CLASSICAL CEPHEIDS primary distance indicators

Mass discrepancy problem for double mode Cepheids pulsational masses  evolutionary masses

Petersen Diagram (P1/P0 vs logP0 ) for  Scuti stars and double mode Cepheids LAOL & OPAL tables Moskalik i in, 1992 Christensen-Dalsgaard 1993

Mass discrepancy remains ML relation dependence Keller 2008 Z dependence mass loss ? internal mixing ? Keller, Wood 2006

double mode Cepheids models result from ignoring bouyancy in convectively stable layers ! Smolec R., Moskalik P., 2008 Growth rates: 0,1- for the fundamental mode with respect to the first overton, 1,0- for the first overton double mode solution is not found !

another interesting facts (OGLE):  nonradial modes in Classical Cepheids  Blazhko Cepheids  1O/3O double-mode Cepheids  single mode 2O Cepheids  triple-mode Cepheids  eclipsing binary systems containing Cepheids Udalski, Soszyński Kołaczkowski, Moskalik, Mizerski

Period–luminosity diagrams for Classical Cepheids in the LMC OGLE Data Soszyński et al. 2008

B type main sequence pulsators M>8M - progenitors of Type II Supernova (most  Cep’s) M<8M – form CNO elements (most SPB stars)

 Cep and SBB stars in Magellanic Clouds Pigulski, Kołaczkowski (2002) Kołaczkowski, 2004, PhD Kołaczkowski et al. (2006) Karoff et al. (2008) LMC Z=0.008 SMC Z=0.004

Pamyatnykh, Ziomek

Miglio, Montalban, Dupret

 problem of mode excitation  uncertainties in opacity and element distribution  extent of overshooting distance  estimate of the interior rotation rate

Dziembowski, Pamyatnykh 2008

sdB stars  core helium burning phase  thin hydrogen envelope  final stage before white dwarfs

sdB PULSATORS Charpinet et al. 1996 – theoretical predication Kilkenny et al. 1997 – observational evidence Green et al. 2003 – long period oscillations Fontaine et al. 2003 – iron accumulation in Z-bump Fontaine et al. 2006 – including radiative levitation

Inner structure and origin ?  single star evolution  binary star evolution -- common envelope evolution -- stable Roche-lobe overflow -- the merge of two He WD stars

sdO stars  C/O core  helium burning shell phase

sdO PULSATORS Woudt, Kilkenny, Zietsman et al. 2006 SDSS object: 13 independent frequencies (P=60-120 s) Rodriguez-Lopez, Ulla, Garrido, 2007 two pulsating candidates in their search (P=500s and 100 s) Rodriguez-Lopez, Ulla, Garrido, 2007

Iron levitation in the pure hydrogen medium Mode excited in the range P105-120 s

inner structure and origin ? „luminous” sdO  post-AGB stars „compact” sdO  post-EHB objects, descendants of sdBs  He-sdOs – the merger of two He WDs or deleyed core He flash scenario

sdOB pulsators – perfect object for testing diffusion processes hybrid sdOB pulsators - Schuh et al. 2006

Extreme helium stars

strange-mode instability – high L/M ratio Detection of variability in hydrogen deficient Bp supergiants: V652 Her (P=0.108d), V2076 Oph (P=0.7-1.1d)– Landlot 1975 strange-mode instability – high L/M ratio Z-bump instability Jeffery 2008

Origin and connection (if any) between normal and the He-rich stars

helium-rich sdB star Pulsation in high order g-modes such modes should be stable Ahmad, Jeffery 2005

Hot DQ White Dwarf stars Carbon atmospheres with little or no trace of H and He new sequence of post-AGB evolution

Dufour, Liebert, Fontaine, Behara, 2007, Nature 450, 522 White dwarf stars with carbon atmospheres Six hot DQ White Dwarfs

a new class variable white dwarfs Montgomery et al. 2008, ApJ 678, L51 SDSS J142625.71575218.3: A Prototype for a new class variable white dwarfs P=417.7 [s] from time-series potometry Period [s] 417 208 83 new class of pulsating carbon-atmosphere WDs (DQVs) or first cataclysmic variable with a carbon-dominated spectrum

Fontaine, Brassard, Dufour, 2008, A&A 483, L1 Might carbon-atmosphere white dwarfs harbour a new type of pulsating star? Unstable low-order g-modes for models with Teff from 18 400 K to 12 600 K, log g = 8.0, X(C) = X(He) = 0.5 Pulsation in hotter models can be excited if surface gravity is increased or if convective is more efficient Dufour, Fontaine et al. 2008, ApJ 683, L167 SDSS J142625.71575218.3: The first pulsating white dwarf with a large detectable magnetic field

EVOLUTION OF PLANETARY SYSTEMS Planets around oscillating solar type stars e.g.  Ara Planets around compact pulsators V391 Peg, Silvotti et al. 2007

SOME THEORETICAL KEY PROBLEMS

OPACITIES determine the transport of radiation through matter (T,, Xi)

LAOL (Los Alamos Opacity Library) till ~1990 Simon (1982) suggestion that the opacity were at fault OPAL (OPAcity Library) F.J. Rogers, C.A. Iglesias i in. 1990 ApJ 360, 221 1992 ApJ 397, 717; ApJS 79, 507 1994 Science 263, 50 1996 ApJ 456, 902 OP (Opacity Project) International team led by M.J. Seatona 1993 MNRAS 265, L25 1996 MNRAS 279, 95 2005 MNRAS 360, 458, MNRAS 362, L1

Opacity in the  Cephei model (M=12 M, X=0.70, Z=0.02): OP (Seaton et al.) vs. OPAL (Livermore) vs. LAOL (Los Alamos) (< 1991) A. A. Pamyatnykh

 (OPAL) as a function of logT and log/T63 (T6 =T/106) C/O bump Pamyatnykh 1999, AcA 49, 119

CONESQUENCES OF Z-BUMP  Seismic model of the Sun improved  Cepheids mass discrepancy solved  pulsation of B type MS stars explained  sdB and sdO pulsation  pulsation of some extreme He stars OSCILLATION FREQUENCIES TEST OF STELLAR OPACITY

Asplund, Grevesse, Sauval 2004, 2005 NEW SOLAR CHEMICAL COMPOSITION Asplund, Grevesse, Sauval 2004, 2005

Comparison of the old and new solar composition A. A. Pamyatnykh

better agreement of solar metallicity with its neighbourhood No problem with B main sequence pulsators Pamyatnykh (2007): more Fe relative to CNO For AGS04 galactic beat Cepheid models are in better agreement with observations Buchler, Szabo 2007 Reduction of the lithium depletion in pre-main sequence stellar models gives better agreement with observations, Montalban,D’Antona 2006

Conspiracy at work: better is worse Basu & Antia, 2007, astro-ph0711.4590

ROTATION

Achernar: the ratio of the axes is 1.56 ± 0.05

1. Structure (spherical symetry broken) 2. mixing (meridional circulation, shear instabilities, diffusion, transport, horizontal turbulence) distribution of internal angular momentum (the rotation velocity at different depths) 3. mass loss from the surface enhanced by the rapid rotation (the centrifugal effect) Laplace, Jacobi, Lioville, Riemann, Poincare, Kelvin, Jeans, Eddington, von Zeipel, Lebovitz, Lyttleton, Schwarzachild, Chandrasekhar, Kippenhahn, Weigert, Sweet, Öpik, Tassoul, Roxgurgh, Zahn, Spruit, Deupree,Talon, Maynet, Maeder, Mathis and many others

Evolutionary tracks for non–rotating and rotating models Maynet, Maeder, 2000

The evolution of (r) during the MS evolution of a 20M star Maynet, Maeder, 2000

Stars can reach the break-up velocity M=20 Z=0.004 Maynet, Maeder, 2000

Soufi, Goupil, Dziembowski 1998 EFFECTS OF ROTATION ON PULSATION The third order expression for a rotationally split frequency Goupil et al. 2000 Dziembowski, Goode 1992 Soufi, Goupil, Dziembowski 1998 Mathis

M=1.8 M, Teff=7515 K, Vrot=92 km/s. Pamyatnykh 2003

EFFECTS OF ROTATION ON PULSATION j - k   ; j = k 2 ; mj = mk ( >> ) rotational mode coupling    perturbation approach fails

rotational mode coupling eigenfunction of an individual mode is a linear combination ak - contributions of the k-modes to the coupled mode Soufi, Goupil, Dziembowski 1998 complex amplitude of the flux variation Daszyńska-Daszkiewicz et al. 2002

Description of slow modes ( ~ )  the traditional approximation Townsend(2003)  Expansion in Legendre function series Lee, Saio (1997)  2D code (Savonije 2007)

Rotation confines pulsation towards the stellar equator Townsend 1997 Hough functions

Rotation complicates identification of pulsational modes diagnostic diagrams become dependent on (i,m,Vrot) Coupled modes: Daszyńska-Daszkiewicz et al. 2002 Slow modes: Townsend 2003, Daszyńska-Daszkiewicz et al. 2007

J. Christensen-Dalsgaard Solar rotation J. Christensen-Dalsgaard

The rotational splitting kernel, K  the =(r) profile For the  Eri model from Pamyatnykh, Handler, Dziembowski, 2004 The rotation rate increases inward, e.g. Goupil, Michel, Lebreton, Baglin 1993 (GX Peg) Dziembowski, Jerzykiewicz 1996 (16 Lac) Aerts, Toul, Daszynska et al. 2003 (V836 Cen) Pamyatnykh, Handler, Dziembowski, 2004 ( Eri) Dziembowski, Pamyatnykh 2008 ( Eri,12 Lac)

Dziembowski & Pamyatnykh 1991, A&A 248, L11 Modes which are largely trapped in the region surrounding the convective core boundary can measure the extend of the overshooting. Ek=2 2 V836 Cen – first evidence of the core overshooting in  Cep star Aerts, Toul, Daszyńska et al., 2003 , Science 300, 1926

Miglio, Montalban, Noels, Eggenberger 2008 Properties of high order g-modes in SPB and  Dor stars Effects of mixing processes on P models of 1.6M with Xc=0.3, =1

IMPACT OF PULSATION ON ROTATIONAL EVOLUTION Talon, Charbonnel 2005 Internal gravity waves contribute to braking the rotation in the inner regions of low mass stars Townsend, MacDonald 2008 Pulsation modes can redistribute angular momentum and trigger shear-instability mixing in the  zone The evolution of  in the  gradient zone transport by (,m)=(4,-4) g-modes

COVECTION  Convection transports energy  Mixing and overshooting convective flows  convection affects stellar spectra  stochastic convective motions excite stellar oscillation  role of convection in heating of stellar chromospheres  Convection + differential rotation  stellar activity

MLT theory of stellar convection Böhm-Vitense 1958 full-spectrum turbulence theory of convection Canuto, Goldman, Mazzitelli 1996 (CGM)

Fractional heat flux carried by covection in the local MLT and in the Gough’s nonlocal, time-dependent convection formalisms, M=1.8 M, log Teff = 3.860, log L = 1.170

3D versus 1D Radiative layer between two convection zones is mixed main-sequence A-type star (Teff =8000 K, log g =4.00, [M/H]=0) H+HeI convection zone vertical velocity [km/s] HeII convection zone Radiative layer between two convection zones is mixed Steffen M. 2007 IAUS 239, 36

Pulsating stars with „convection problem”  Scuti  Doradus Classical Cepheids RR Lyrae Red giants White dwarfs (V777Her, ZZ Cet)

Convective–flux freezing approximation Fconv=const during pulsation cycle

pulsation-convection interactions Unno 1967 Gough 1977 Solar-like stars – Houdek, Goupil, Samadi  Scuti,  Doradus -Xiong, Houdek, Dupret, Grigahcène, Moya Classical Cepheids, RR Lyr – Feuchtinger, Stellingwerf, Buchler, Kollath, Smolec Pulsating Red Giants – Xiong, Deng, Cheng DB (V777 Her) white dwarfs – Quirion, Dupret

M =1.6 M, Teff = 6665 K,  = 1.8, mode =0, p1 Dupret et al. 2004

MASS LOSS Important for late evolutionary phases and for massive stars Hot stars  Radiation-driven wind Cool and luminous stars Dust-driven wind mostly empirical mass-loss formulae are used

pulsation and mass loss coupling Red giants (Mira and SR) – Wood 1979, Castor 1981 mass loss: stellar pulsation & radiation pressure on dust grains dM/dt - P relation Knapp et al. 1998

pulsation and mass loss coupling Massive stars (OB MS, W-R stars), LBV Howarth et al. 1993 – wind variability in  Oph Kaufer 2006 – B0 supergiant (HD 64760) pulsation beat period observed in H Owocki et al. 2004 Townsend 2007

GW Vir stars Constraints on mass loss from the red-edge position different mass loss laws Quirion, Fontaine, Brassard 2007

not only pulsation frequencies can probe stellar interior photometric and spectroscopic observables

input from pulsation calculation: Theoretical photometric amplitudes and phases: input from pulsation calculation: linear nonadiabatic theory: the f parameter the ratio of the bolometric flux variation to the radial displacement at the photosphere level input from atmosphere models: derivatives of the monochromatic flux over Teff and g limb darkening coefficients: h(Teff , g)

The flux derivatives over Teff and log g depend on:  microturbulence velocity, t  metallicity, [m/H]  models of stellar atmospheres, NLTE effects

The f parameter is very sensitive to:  global stellar parameters  chemical composition  element mixture, mixing processes  opacity  subphotospheric convection

simultaneous determination of  and f from observations multicolor photometry + radial velocity data simultaneous determination of  and f from observations

Comparison of theoretical and empirical f values yields constraints on MEAN STELLAR PARAMETERS STELLAR ATMOSPHERES INPUT PHYSICS

f - a new asteroseismic probe sensitive to subphotospheric layers and complementary to pulsation frequency

Ocillation spectrum of FG Vir 67 independent frequencies ! Breger et al. 2005

Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653 Empirical and theoretical f values. Model: MLT, convective flux freezing approximation Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653

Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653 Empirical and theoretical f values. Model: non-local, time-dependent formulation of MLT due to Guenter Houdek Daszyńska-Daszkiewicz et al. 2005, A&A 438, 653

OSCILLATION SPECTRUM OF  ERI Jerzykiewicz i in., 2005, MNRAS 360, 619 12 independent frequencies Jerzykiewicz i in., 2005, MNRAS 360, 619

Comparison of the empirical and theoretical f values for the dominant frequency (=0 mode) of  Eri Daszyńska-Daszkiewicz et al. 2005, A&A 441, 641

Seismic model with the new solar composition added DIFFUSION ???

CONCLUSIONS  more realistic treatment of macro- and microphysics in stellar modelling  more parallel photometric and spectroscopic observations  Ideal seismic stellar models should account not only for all measured frequencies but also for associated pulsation characteristics  Asteroseismology helps: - to solve the equation observation =theory - to avoid more date=less understanding